1. Field of the Invention
This invention relates to a container filling nozzle.
2. Description of the Prior Art
Various container filling nozzles are known from for example, British Patent 2095584, Federal German Patent Application Publication 2107647, European Patent Application Publication 199538, and U.S. Pat. No. 3,186,451.
British Patent 2095584B discloses a valve unit to be used more especially in packaging machine of the type in which sealed nonreturnable packages for diary products such milk, yoghurt and the like, are filled one at a time by means of a metering pump. The unit comprises a check valve and a flexible nozzle having a slit normally urged closed by the resilience of the material. The flexible nozzle is disposed a short distance downstream of the check valve and the two items co-operate so as to prevent any after-dripping between pumping strokes. This is achieved in that the check valve with the help of a piston component, after the completed pumping stroke, creates a vacuum in the liquid filled, chamber, this vacuum affecting the flexible nozzle so that it closes rapidly and effectively. The nozzle is of a substantially cylindrical or truncated cone main shape which, however, is disturbed at the lower end of the nozzle by four recesses arranged symmetrically, which together give the lower extremity of the nozzle, which is the outlet extremity, the form of a cross, the outlet slit being of a correspondingly cruciform shape. In the angles of the cruciform shape of the outlet slit, the four recesses form four substantially triangular lugs which, because of the flexibility of the material, are capable of being folded out to a relatively wide open position, when the liquid passes through the nozzle. To obtain the desired flexibility of the nozzle, the nozzle is manufactured from soft plastics or rubber of a hardness of 25.degree.-40.degree. Shore. Since the nozzle is intended primarily for dairy products, the material selected is suitable for use jointly with foodstuffs, e.g. nitrile or silicone rubber.
It is desirable to avoid the need for a vacuum-creating piston component by employing solely the resilience of the material to obtain a good closure of the outlet slit. However, in order to obtain sufficient flexibility of the four lips of the nozzle, the nozzle wall needs to be made reasonably thin. Unfortunately, in practice, owing to the softness of the elastomeric material and to variations in the Shore hardness during manufacturing, the nozzle lips come unexpectedly open during their intended closed condition, so that the product being filled leaks out.